The present invention relates to the field of differentials for vehicle drive trains and pertains particularly to positively locking differentials for motor vehicles.
Land vehicles, such as automobiles, trucks, buses and the like, typically utilize what has become known as an open differential for the final drive system. An automotive differential is a mechanical assembly, often a system of gears, which is located in the driving axle of a vehicle. It applies power to the wheels while at the same time allowing a difference in their rotational speeds; this difference occurs when the vehicle turns because the outside wheel rotates faster than the inside wheel due to its larger turning radius. Differentials accomplish this function in various ways, depending on their particular designs.
Differentials go back to the beginnings of the automotive era, but many of them had major traction problems in difficult terrain. Differentials have evolved into two broad classes: (1) Standard, or "open" differentials, and (2) Traction-adding differentials. Open differentials are by far the most common because they are inexpensive and do a good job for the majority of vehicles on the highway. However, open differentials have one major drawback: They can provide only limited power in marginal traction situations. To overcome this drawback, mechanical traction-adding differentials have been developed. These types of differentials are divided into two classes: (1) Limited Slip differentials, and (2) Locking differentials. Limited slip differentials are furler divided into two general classes: (1) Clutch type and (2) Gear type. Locking differentials also are further divided into two general classes: (1) Automatic and (2) Manual (activated by the driver). This invention is concerned primarily with automatic locking differentials, since they are the most widely used lockers and exist in a variety of designs. Other types of traction-enhancing devices and systems also have been developed, notably viscous coupling differentials and electronic traction control (ETC); however, these and other exotic designs are not mechanical lockers. Many designs have been tried over the years to overcome these traction problems, and some were produced either as factory-installed units or as after-market devices. While many of them have been satisfactory in many respects, they also have some drawbacks. Among these drawbacks are complexity, lack of reliability, cost, and adverse vehicle handling characteristics. Thus, a need exists for a simple, inexpensive, reliable and effective locking differential.